<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <style>
        * {
            margin: 0;
            padding: 0;
            border: 0;
            box-sizing: border-box;
        }
        div{
            background-color: #fff;
        }
        body{
            text-align: center;
        }

        .container {
            width: auto;
            height: 400px;
            margin: 0 auto;
            border: 2px solid #e74f4d;
            overflow: hidden;

        }

        .container2{
            width: 45%;
            height: 90%;
            float: left;
            margin: 20px;
            border: 2px solid green;
        }

        .container3 {
            width: 35%;
            height: 90%;
            float: left;
            margin: 20px;
            border: 2px solid blue;
        }

        .container4 {
            width: 25%;
            height: 90%;
            float: left;
            margin: 20px;
            border: 2px solid #e74f4d;
        }

        button{
            width: 150px;
            height: 50px;
            margin: 20px auto;
            display: block;
            border: 2px solid #e74f4d;
            text-align: center;
            line-height: 50px;
            background-color: #fff;
        }

        input{
            display: inline-block;
            width: 200px;
            height: 50px;
            border: 2px solid #e74f4d;
        }
        #add {
            width: 150px;
            height: 50px;
            display: inline-block;
            border: 2px solid #e74f4d;
            text-align: center;
            line-height: 50px;
            background-color: #fff;
            margin-bottom: 20px;
        }
    </style>
</head>
<body>

<button id="traversal">开始遍历</button>
<input type="text" id="key">
<button id="add">add</button>

<div class="container">
    <div class="container2">123
        <div class="container3">
            <div class="container4">hello</div>
            <div class="container4">world</div>
        </div>
        <div class="container3">
            <div class="container4">hello</div>
            <div class="container4">56</div>
        </div>
    </div>
    <div class="container2">real
        <div class="container3">
            <div class="container4">hello</div>
            <div class="container4">17323</div>
        </div>
        <div class="container3">
            <div class="container4">how </div>
            <div class="container4">you</div>
        </div>
    </div>
</div>

<script src="task.js"></script>
</body>
</html>